The second ionization potential of Be is 17.98 eV. If the outermost electron in ${\mathrm{Be}}^{+}$ is assumed to move in a spherical orbit with a central field of effective nuclear charge (${\mathrm{Z}}_{\mathrm{eff}}$) consisting of nucleus and other electrons, by how many units of charge is the nucleus shielded by other electrons? [Energy of electron in the first orbit of H-atom = —13.6 eV]

1.   2.0 unit

2.  0.5 unit

3.  1.0 unit

4.  1.7 unit

The charge on the electron and proton are reduced to $\frac{2}{3}\mathrm{rd}$ of their original values. Let the present value of the Rydberg constant of H-atom be R, then the new value of the Rydberg constant will be

$1. \frac{2\mathrm{R}}{3}$
$2. \frac{4\mathrm{R}}{9}$
$3. \frac{8\mathrm{R}}{27}$
$4. \frac{16\mathrm{R}}{81}$

Of the following transitions in hydrogen atom, the one which gives an absorption line of lowest frequency is:

1.  n = 1 to n = 2

2.  n = 3 to n = 8

3.  n = 2 to n = 1

4.  n = 8 to n = 3

The wavelength of the spectral line obtained in the spectrum of ${\mathrm{Li}}^{+2}$
when the transition takes place between levels whose sum is 4 and the difference is 2, will be:

1.  11.4 x ${10}^{-6}$ cm

2.  1.14 x ${10}^{-6}$cm

3.  0.114 x ${10}^{-6}$ cm

4.  1.14 x ${10}^{-8}$ cm

In the transition of an electron in an atom, its kinetic energy changes from y to $\frac{y}{4}$. The change in potential energy will be -

1. \(\frac{-3}{8} y\)
2. \({{3}\over{2}}y\)
3. \({{3}\over{4}}y\)
4. \(-{{3}\over{4}}y\)

The ratio of the area of the orbit of the first excited state of an electron to the area of the orbit of ground level for hydrogen atom will be

1.  4:1

2.  8:1

3.  16:1

4.  2:1

A photon with an initial frequency of \(10^{11}~\mathrm{Hz}\) scatters off an electron at rest. Its final frequency is \(0.9 \times10^{11}~\mathrm{Hz}.\) The speed of scattered electron is close to: 

Photons of wavelength 4000  $A^o$ are used to break ${\mathrm{l}}_2$ molecules. The percentage of energy converted to the kinetic energy of atoms will be :

(bond dissociation energy of the molecule is 246.5 kJ/mol)

1.  12%

2.  8%

3.  26%

4.  17%

Which of the following sets of quantum numbers represent an impossible arrangement - 

       n   l    m     s

(1)  3   2   -2   (+)1/2

(2)  4   0   0    (-)1/2

(3)  3   2   -3   (+)1/2

(4)  5   3   0   (-)1/2

Correct set of four quantum numbers for the outermost electron of rubidium (Z=37) is:

(1) 5, 0, 0, 1/2

(2) 5, 1, 0, 1/2

(3) 5, 1, 1, 1/2

(4) 6, 0, 0, 1/2